An apparatus for the production of a flowable reaction mixture comprising reservoirs for the reaction components, supply lines with metering pumps leading from said reservoirs to a mixing head which has a mixing chamber, injection openings connected to said supply lines and opening into said mixing chamber, and an outlet opening to which is connected an elastic sleeve whose cross section may be varied is known from U.S. Pat. No. 3,220,801. In that apparatus, the pressure in the mixing chamber, which affects the size of the cells of the foam which is forming, is adjusted by changes in the throughflow cross section of the outlet tube leading from the mixing chamber. A small pressure chamber between the outlet tube and a supporting pipe around it is charged with a compression agent, pressing the tube against the ring shoulders projecting from the supporting pipe which create the chamber, thus reducing the cross section of the tube.
This apparatus is not economical for high speed molding, however, since rinsing procedures would be necessary between the individual filling operations. The apparatus may only be used for applications operating continuously for a long time, such as block foam installations or double conveyor belt installations.
An object of the present invention is to provide an apparatus for producing a flowable reaction mixture which may be easily cleaned and which allows the pressure in the mixing chamber to be controlled and the reaction mixture to issue from the outlet pipe in a laminar flow. This is particularly important when introducing the reaction mixture into molding tools in order to avoid the harmful impact of air and to achieve a closed flow front which expands as evenly as possible.
In the apparatus according to the present invention, the throughflow cross section of the outlet tube may be adjusted by laterally deflecting the outlet tube during the mixing phase, as a result of which, the pressure in the mixing chamber may be controlled. Further, as a result of the deflection of the outlet tube, even while retaining the throughflow cross section, a flow path may be formed such that the flow is substantially stabilized in the outlet pipe. An additional advantage is realized since remnants of mixture may be removed from the outlet tube using an ejection piston, as in the case of known ejection piston mixing heads having rigid outlet pipes (U.S. Pat. Nos. 2,890,836 and 4,141,470).